Conventionally, for a multicarrier communication in which a plurality of subcarriers are used for transmitting data in parallel, there has been a communication method in which a primary modulation method (in other words, “modulation scheme”) is selected for each subcarrier according to a preconfigured transmission status.
In this communication method, a plurality of adaptive modulation blocks are provided for each subcarrier. A transmission status of each adaptive modulation block is divided into a plurality of levels (for example, 4 levels) according to a set of thresholds. For each level of the transmission status, an optimal primary modulation method is selected for transmission. For example, when the transmission status is above the third threshold, a signal is transmitted with 64QAM; when the transmission status is above the second threshold, a signal is transmitted with 16QAM; when the transmission status is above the first threshold, a signal is transmitted with QPSK; and when the transmission status is below the first threshold, it is treated as a dummy state and no signal is transmitted.
As described above, more data are transmitted on a subcarrier with a good transmission status, and less data are transmitted on a subcarrier with a bad transmission status, thereby making it possible to transmit a high quality signal at a high speed (for example, see Japanese Laid-Open Patent Publication H10-247955).